Conventional edge-emitting semiconductor devices such as lasers and semiconductor optical amplifiers (SOA's) usually comprise a substrate, on which epitaxial layers of varying alloy compositions, carrier types and carrier densities have grown. These various layers are used to define the optical waveguide and the gain region of the device, which are designed to support amplification and emission of radiation in a single spatial mode. Typically, for high power devices, the dimensions of the cross-sectional area of the single spatial mode are a few micrometers in the direction parallel to the epitaxial layers (the lateral direction) and a fraction of a micrometer perpendicular to those layers (the transverse direction).